/*
** $Id: lstrlib.c,v 1.254 2016/12/22 13:08:50 roberto Exp $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/

#define lstrlib_c
#define LUA_LIB

#include "lprefix.h"


#include <ctype.h>
#include <float.h>
#include <limits.h>
#include <locale.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"


/*
** maximum number of captures that a pattern can do during
** pattern-matching. This limit is arbitrary, but must fit in
** an unsigned char.
*/
#if !defined(LUA_MAXCAPTURES)
#define LUA_MAXCAPTURES     32
#endif


/* macro to 'unsign' a character */
#define uchar(c)    ((unsigned char)(c))


/*
** Some sizes are better limited to fit in 'int', but must also fit in
** 'size_t'. (We assume that 'lua_Integer' cannot be smaller than 'int'.)
*/
#define MAX_SIZET   ((size_t)(~(size_t)0))

#define MAXSIZE  \
    (sizeof(size_t) < sizeof(int) ? MAX_SIZET : (size_t)(INT_MAX))




static int str_len(lua_State *L)
{
    size_t l;
    luaL_checklstring(L, 1, &l);
    lua_pushinteger(L, (lua_Integer)l);
    return 1;
}


/* translate a relative string position: negative means back from end */
static lua_Integer posrelat(lua_Integer pos, size_t len)
{
    if (pos >= 0) return pos;
    else if (0u - (size_t)pos > len) return 0;
    else return (lua_Integer)len + pos + 1;
}


static int str_sub(lua_State *L)
{
    size_t l;
    const char *s = luaL_checklstring(L, 1, &l);
    lua_Integer start = posrelat(luaL_checkinteger(L, 2), l);
    lua_Integer end = posrelat(luaL_optinteger(L, 3, -1), l);
    if (start < 1) start = 1;
    if (end > (lua_Integer)l) end = l;
    if (start <= end)
        lua_pushlstring(L, s + start - 1, (size_t)(end - start) + 1);
    else lua_pushliteral(L, "");
    return 1;
}


static int str_reverse(lua_State *L)
{
    size_t l, i;
    luaL_Buffer b;
    const char *s = luaL_checklstring(L, 1, &l);
    char *p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++)
        p[i] = s[l - i - 1];
    luaL_pushresultsize(&b, l);
    return 1;
}


static int str_lower(lua_State *L)
{
    size_t l;
    size_t i;
    luaL_Buffer b;
    const char *s = luaL_checklstring(L, 1, &l);
    char *p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++)
        p[i] = tolower(uchar(s[i]));
    luaL_pushresultsize(&b, l);
    return 1;
}


static int str_upper(lua_State *L)
{
    size_t l;
    size_t i;
    luaL_Buffer b;
    const char *s = luaL_checklstring(L, 1, &l);
    char *p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++)
        p[i] = toupper(uchar(s[i]));
    luaL_pushresultsize(&b, l);
    return 1;
}


static int str_rep(lua_State *L)
{
    size_t l, lsep;
    const char *s = luaL_checklstring(L, 1, &l);
    lua_Integer n = luaL_checkinteger(L, 2);
    const char *sep = luaL_optlstring(L, 3, "", &lsep);
    if (n <= 0) lua_pushliteral(L, "");
    else if (l + lsep < l || l + lsep > MAXSIZE / n)  /* may overflow? */
        return luaL_error(L, "resulting string too large");
    else
    {
        size_t totallen = (size_t)n * l + (size_t)(n - 1) * lsep;
        luaL_Buffer b;
        char *p = luaL_buffinitsize(L, &b, totallen);
        while (n-- > 1)    /* first n-1 copies (followed by separator) */
        {
            memcpy(p, s, l * sizeof(char));
            p += l;
            if (lsep > 0)    /* empty 'memcpy' is not that cheap */
            {
                memcpy(p, sep, lsep * sizeof(char));
                p += lsep;
            }
        }
        memcpy(p, s, l * sizeof(char));  /* last copy (not followed by separator) */
        luaL_pushresultsize(&b, totallen);
    }
    return 1;
}


static int str_byte(lua_State *L)
{
    size_t l;
    const char *s = luaL_checklstring(L, 1, &l);
    lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), l);
    lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), l);
    int n, i;
    if (posi < 1) posi = 1;
    if (pose > (lua_Integer)l) pose = l;
    if (posi > pose) return 0;  /* empty interval; return no values */
    if (pose - posi >= INT_MAX)  /* arithmetic overflow? */
        return luaL_error(L, "string slice too long");
    n = (int)(pose -  posi) + 1;
    luaL_checkstack(L, n, "string slice too long");
    for (i = 0; i < n; i++)
        lua_pushinteger(L, uchar(s[posi + i - 1]));
    return n;
}


static int str_char(lua_State *L)
{
    int n = lua_gettop(L);  /* number of arguments */
    int i;
    luaL_Buffer b;
    char *p = luaL_buffinitsize(L, &b, n);
    for (i = 1; i <= n; i++)
    {
        lua_Integer c = luaL_checkinteger(L, i);
        luaL_argcheck(L, uchar(c) == c, i, "value out of range");
        p[i - 1] = uchar(c);
    }
    luaL_pushresultsize(&b, n);
    return 1;
}


static int writer(lua_State *L, const void *b, size_t size, void *B)
{
    (void)L;
    luaL_addlstring((luaL_Buffer *) B, (const char *)b, size);
    return 0;
}


static int str_dump(lua_State *L)
{
    luaL_Buffer b;
    int strip = lua_toboolean(L, 2);
    luaL_checktype(L, 1, LUA_TFUNCTION);
    lua_settop(L, 1);
    luaL_buffinit(L, &b);
    if (lua_dump(L, writer, &b, strip) != 0)
        return luaL_error(L, "unable to dump given function");
    luaL_pushresult(&b);
    return 1;
}



/*
** {======================================================
** PATTERN MATCHING
** =======================================================
*/


#define CAP_UNFINISHED  (-1)
#define CAP_POSITION    (-2)


typedef struct MatchState
{
    const char *src_init;  /* init of source string */
    const char *src_end;  /* end ('\0') of source string */
    const char *p_end;  /* end ('\0') of pattern */
    lua_State *L;
    int matchdepth;  /* control for recursive depth (to avoid C stack overflow) */
    unsigned char level;  /* total number of captures (finished or unfinished) */
    struct
    {
        const char *init;
        ptrdiff_t len;
    } capture[LUA_MAXCAPTURES];
} MatchState;


/* recursive function */
static const char *match(MatchState *ms, const char *s, const char *p);


/* maximum recursion depth for 'match' */
#if !defined(MAXCCALLS)
#define MAXCCALLS   200
#endif


#define L_ESC       '%'
#define SPECIALS    "^$*+?.([%-"


static int check_capture(MatchState *ms, int l)
{
    l -= '1';
    if (l < 0 || l >= ms->level || ms->capture[l].len == CAP_UNFINISHED)
        return luaL_error(ms->L, "invalid capture index %%%d", l + 1);
    return l;
}


static int capture_to_close(MatchState *ms)
{
    int level = ms->level;
    for (level--; level >= 0; level--)
        if (ms->capture[level].len == CAP_UNFINISHED) return level;
    return luaL_error(ms->L, "invalid pattern capture");
}


static const char *classend(MatchState *ms, const char *p)
{
    switch (*p++)
    {
    case L_ESC:
    {
        if (p == ms->p_end)
            luaL_error(ms->L, "malformed pattern (ends with '%%')");
        return p + 1;
    }
    case '[':
    {
        if (*p == '^') p++;
        do    /* look for a ']' */
        {
            if (p == ms->p_end)
                luaL_error(ms->L, "malformed pattern (missing ']')");
            if (*(p++) == L_ESC && p < ms->p_end)
                p++;  /* skip escapes (e.g. '%]') */
        }
        while (*p != ']');
        return p + 1;
    }
    default:
    {
        return p;
    }
    }
}


static int match_class(int c, int cl)
{
    int res;
    switch (tolower(cl))
    {
    case 'a' :
        res = isalpha(c);
        break;
    case 'c' :
        res = iscntrl(c);
        break;
    case 'd' :
        res = isdigit(c);
        break;
    case 'g' :
        res = isgraph(c);
        break;
    case 'l' :
        res = islower(c);
        break;
    case 'p' :
        res = ispunct(c);
        break;
    case 's' :
        res = isspace(c);
        break;
    case 'u' :
        res = isupper(c);
        break;
    case 'w' :
        res = isalnum(c);
        break;
    case 'x' :
        res = isxdigit(c);
        break;
    case 'z' :
        res = (c == 0);
        break;  /* deprecated option */
    default:
        return (cl == c);
    }
    return (islower(cl) ? res : !res);
}


static int matchbracketclass(int c, const char *p, const char *ec)
{
    int sig = 1;
    if (*(p + 1) == '^')
    {
        sig = 0;
        p++;  /* skip the '^' */
    }
    while (++p < ec)
    {
        if (*p == L_ESC)
        {
            p++;
            if (match_class(c, uchar(*p)))
                return sig;
        }
        else if ((*(p + 1) == '-') && (p + 2 < ec))
        {
            p += 2;
            if (uchar(*(p - 2)) <= c && c <= uchar(*p))
                return sig;
        }
        else if (uchar(*p) == c) return sig;
    }
    return !sig;
}


static int singlematch(MatchState *ms, const char *s, const char *p,
                       const char *ep)
{
    if (s >= ms->src_end)
        return 0;
    else
    {
        int c = uchar(*s);
        switch (*p)
        {
        case '.':
            return 1;  /* matches any char */
        case L_ESC:
            return match_class(c, uchar(*(p + 1)));
        case '[':
            return matchbracketclass(c, p, ep - 1);
        default:
            return (uchar(*p) == c);
        }
    }
}


static const char *matchbalance(MatchState *ms, const char *s,
                                const char *p)
{
    if (p >= ms->p_end - 1)
        luaL_error(ms->L, "malformed pattern (missing arguments to '%%b')");
    if (*s != *p) return NULL;
    else
    {
        int b = *p;
        int e = *(p + 1);
        int cont = 1;
        while (++s < ms->src_end)
        {
            if (*s == e)
            {
                if (--cont == 0) return s + 1;
            }
            else if (*s == b) cont++;
        }
    }
    return NULL;  /* string ends out of balance */
}


static const char *max_expand(MatchState *ms, const char *s,
                              const char *p, const char *ep)
{
    ptrdiff_t i = 0;  /* counts maximum expand for item */
    while (singlematch(ms, s + i, p, ep))
        i++;
    /* keeps trying to match with the maximum repetitions */
    while (i >= 0)
    {
        const char *res = match(ms, (s + i), ep + 1);
        if (res) return res;
        i--;  /* else didn't match; reduce 1 repetition to try again */
    }
    return NULL;
}


static const char *min_expand(MatchState *ms, const char *s,
                              const char *p, const char *ep)
{
    for (;;)
    {
        const char *res = match(ms, s, ep + 1);
        if (res != NULL)
            return res;
        else if (singlematch(ms, s, p, ep))
            s++;  /* try with one more repetition */
        else return NULL;
    }
}


static const char *start_capture(MatchState *ms, const char *s,
                                 const char *p, int what)
{
    const char *res;
    int level = ms->level;
    if (level >= LUA_MAXCAPTURES) luaL_error(ms->L, "too many captures");
    ms->capture[level].init = s;
    ms->capture[level].len = what;
    ms->level = level + 1;
    if ((res = match(ms, s, p)) == NULL) /* match failed? */
        ms->level--;  /* undo capture */
    return res;
}


static const char *end_capture(MatchState *ms, const char *s,
                               const char *p)
{
    int l = capture_to_close(ms);
    const char *res;
    ms->capture[l].len = s - ms->capture[l].init;  /* close capture */
    if ((res = match(ms, s, p)) == NULL)  /* match failed? */
        ms->capture[l].len = CAP_UNFINISHED;  /* undo capture */
    return res;
}


static const char *match_capture(MatchState *ms, const char *s, int l)
{
    size_t len;
    l = check_capture(ms, l);
    len = ms->capture[l].len;
    if ((size_t)(ms->src_end - s) >= len &&
            memcmp(ms->capture[l].init, s, len) == 0)
        return s + len;
    else return NULL;
}


static const char *match(MatchState *ms, const char *s, const char *p)
{
    if (ms->matchdepth-- == 0)
        luaL_error(ms->L, "pattern too complex");
init: /* using goto's to optimize tail recursion */
    if (p != ms->p_end)    /* end of pattern? */
    {
        switch (*p)
        {
        case '(':    /* start capture */
        {
            if (*(p + 1) == ')')  /* position capture? */
                s = start_capture(ms, s, p + 2, CAP_POSITION);
            else
                s = start_capture(ms, s, p + 1, CAP_UNFINISHED);
            break;
        }
        case ')':    /* end capture */
        {
            s = end_capture(ms, s, p + 1);
            break;
        }
        case '$':
        {
            if ((p + 1) != ms->p_end)  /* is the '$' the last char in pattern? */
                goto dflt;  /* no; go to default */
            s = (s == ms->src_end) ? s : NULL;  /* check end of string */
            break;
        }
        case L_ESC:    /* escaped sequences not in the format class[*+?-]? */
        {
            switch (*(p + 1))
            {
            case 'b':    /* balanced string? */
            {
                s = matchbalance(ms, s, p + 2);
                if (s != NULL)
                {
                    p += 4;
                    goto init;  /* return match(ms, s, p + 4); */
                }  /* else fail (s == NULL) */
                break;
            }
            case 'f':    /* frontier? */
            {
                const char *ep;
                char previous;
                p += 2;
                if (*p != '[')
                    luaL_error(ms->L, "missing '[' after '%%f' in pattern");
                ep = classend(ms, p);  /* points to what is next */
                previous = (s == ms->src_init) ? '\0' : *(s - 1);
                if (!matchbracketclass(uchar(previous), p, ep - 1) &&
                        matchbracketclass(uchar(*s), p, ep - 1))
                {
                    p = ep;
                    goto init;  /* return match(ms, s, ep); */
                }
                s = NULL;  /* match failed */
                break;
            }
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':    /* capture results (%0-%9)? */
            {
                s = match_capture(ms, s, uchar(*(p + 1)));
                if (s != NULL)
                {
                    p += 2;
                    goto init;  /* return match(ms, s, p + 2) */
                }
                break;
            }
            default:
                goto dflt;
            }
            break;
        }
        default:
dflt:    /* pattern class plus optional suffix */
            {
                const char *ep = classend(ms, p);  /* points to optional suffix */
                /* does not match at least once? */
                if (!singlematch(ms, s, p, ep))
                {
                    if (*ep == '*' || *ep == '?' || *ep == '-')    /* accept empty? */
                    {
                        p = ep + 1;
                        goto init;  /* return match(ms, s, ep + 1); */
                    }
                    else  /* '+' or no suffix */
                        s = NULL;  /* fail */
                }
                else    /* matched once */
                {
                    switch (*ep)    /* handle optional suffix */
                    {
                    case '?':    /* optional */
                    {
                        const char *res;
                        if ((res = match(ms, s + 1, ep + 1)) != NULL)
                            s = res;
                        else
                        {
                            p = ep + 1;
                            goto init;  /* else return match(ms, s, ep + 1); */
                        }
                        break;
                    }
                    case '+':  /* 1 or more repetitions */
                        s++;  /* 1 match already done */
                        /* FALLTHROUGH */
                    case '*':  /* 0 or more repetitions */
                        s = max_expand(ms, s, p, ep);
                        break;
                    case '-':  /* 0 or more repetitions (minimum) */
                        s = min_expand(ms, s, p, ep);
                        break;
                    default:  /* no suffix */
                        s++;
                        p = ep;
                        goto init;  /* return match(ms, s + 1, ep); */
                    }
                }
                break;
            }
        }
    }
    ms->matchdepth++;
    return s;
}



static const char *lmemfind(const char *s1, size_t l1,
                            const char *s2, size_t l2)
{
    if (l2 == 0) return s1;  /* empty strings are everywhere */
    else if (l2 > l1) return NULL;  /* avoids a negative 'l1' */
    else
    {
        const char *init;  /* to search for a '*s2' inside 's1' */
        l2--;  /* 1st char will be checked by 'memchr' */
        l1 = l1 - l2; /* 's2' cannot be found after that */
        while (l1 > 0 && (init = (const char *)memchr(s1, *s2, l1)) != NULL)
        {
            init++;   /* 1st char is already checked */
            if (memcmp(init, s2 + 1, l2) == 0)
                return init - 1;
            else    /* correct 'l1' and 's1' to try again */
            {
                l1 -= init - s1;
                s1 = init;
            }
        }
        return NULL;  /* not found */
    }
}


static void push_onecapture(MatchState *ms, int i, const char *s,
                            const char *e)
{
    if (i >= ms->level)
    {
        if (i == 0)  /* ms->level == 0, too */
            lua_pushlstring(ms->L, s, e - s);  /* add whole match */
        else
            luaL_error(ms->L, "invalid capture index %%%d", i + 1);
    }
    else
    {
        ptrdiff_t l = ms->capture[i].len;
        if (l == CAP_UNFINISHED) luaL_error(ms->L, "unfinished capture");
        if (l == CAP_POSITION)
            lua_pushinteger(ms->L, (ms->capture[i].init - ms->src_init) + 1);
        else
            lua_pushlstring(ms->L, ms->capture[i].init, l);
    }
}


static int push_captures(MatchState *ms, const char *s, const char *e)
{
    int i;
    int nlevels = (ms->level == 0 && s) ? 1 : ms->level;
    luaL_checkstack(ms->L, nlevels, "too many captures");
    for (i = 0; i < nlevels; i++)
        push_onecapture(ms, i, s, e);
    return nlevels;  /* number of strings pushed */
}


/* check whether pattern has no special characters */
static int nospecials(const char *p, size_t l)
{
    size_t upto = 0;
    do
    {
        if (strpbrk(p + upto, SPECIALS))
            return 0;  /* pattern has a special character */
        upto += strlen(p + upto) + 1;  /* may have more after \0 */
    }
    while (upto <= l);
    return 1;  /* no special chars found */
}


static void prepstate(MatchState *ms, lua_State *L,
                      const char *s, size_t ls, const char *p, size_t lp)
{
    ms->L = L;
    ms->matchdepth = MAXCCALLS;
    ms->src_init = s;
    ms->src_end = s + ls;
    ms->p_end = p + lp;
}


static void reprepstate(MatchState *ms)
{
    ms->level = 0;
    lua_assert(ms->matchdepth == MAXCCALLS);
}


static int str_find_aux(lua_State *L, int find)
{
    size_t ls, lp;
    const char *s = luaL_checklstring(L, 1, &ls);
    const char *p = luaL_checklstring(L, 2, &lp);
    lua_Integer init = posrelat(luaL_optinteger(L, 3, 1), ls);
    if (init < 1) init = 1;
    else if (init > (lua_Integer)ls + 1)    /* start after string's end? */
    {
        lua_pushnil(L);  /* cannot find anything */
        return 1;
    }
    /* explicit request or no special characters? */
    if (find && (lua_toboolean(L, 4) || nospecials(p, lp)))
    {
        /* do a plain search */
        const char *s2 = lmemfind(s + init - 1, ls - (size_t)init + 1, p, lp);
        if (s2)
        {
            lua_pushinteger(L, (s2 - s) + 1);
            lua_pushinteger(L, (s2 - s) + lp);
            return 2;
        }
    }
    else
    {
        MatchState ms;
        const char *s1 = s + init - 1;
        int anchor = (*p == '^');
        if (anchor)
        {
            p++;
            lp--;  /* skip anchor character */
        }
        prepstate(&ms, L, s, ls, p, lp);
        do
        {
            const char *res;
            reprepstate(&ms);
            if ((res = match(&ms, s1, p)) != NULL)
            {
                if (find)
                {
                    lua_pushinteger(L, (s1 - s) + 1);  /* start */
                    lua_pushinteger(L, res - s);   /* end */
                    return push_captures(&ms, NULL, 0) + 2;
                }
                else
                    return push_captures(&ms, s1, res);
            }
        }
        while (s1++ < ms.src_end && !anchor);
    }
    lua_pushnil(L);  /* not found */
    return 1;
}


static int str_find(lua_State *L)
{
    return str_find_aux(L, 1);
}


static int str_match(lua_State *L)
{
    return str_find_aux(L, 0);
}


/* state for 'gmatch' */
typedef struct GMatchState
{
    const char *src;  /* current position */
    const char *p;  /* pattern */
    const char *lastmatch;  /* end of last match */
    MatchState ms;  /* match state */
} GMatchState;


static int gmatch_aux(lua_State *L)
{
    GMatchState *gm = (GMatchState *)lua_touserdata(L, lua_upvalueindex(3));
    const char *src;
    gm->ms.L = L;
    for (src = gm->src; src <= gm->ms.src_end; src++)
    {
        const char *e;
        reprepstate(&gm->ms);
        if ((e = match(&gm->ms, src, gm->p)) != NULL && e != gm->lastmatch)
        {
            gm->src = gm->lastmatch = e;
            return push_captures(&gm->ms, src, e);
        }
    }
    return 0;  /* not found */
}


static int gmatch(lua_State *L)
{
    size_t ls, lp;
    const char *s = luaL_checklstring(L, 1, &ls);
    const char *p = luaL_checklstring(L, 2, &lp);
    GMatchState *gm;
    lua_settop(L, 2);  /* keep them on closure to avoid being collected */
    gm = (GMatchState *)lua_newuserdata(L, sizeof(GMatchState));
    prepstate(&gm->ms, L, s, ls, p, lp);
    gm->src = s;
    gm->p = p;
    gm->lastmatch = NULL;
    lua_pushcclosure(L, gmatch_aux, 3);
    return 1;
}


static void add_s(MatchState *ms, luaL_Buffer *b, const char *s,
                  const char *e)
{
    size_t l, i;
    lua_State *L = ms->L;
    const char *news = lua_tolstring(L, 3, &l);
    for (i = 0; i < l; i++)
    {
        if (news[i] != L_ESC)
            luaL_addchar(b, news[i]);
        else
        {
            i++;  /* skip ESC */
            if (!isdigit(uchar(news[i])))
            {
                if (news[i] != L_ESC)
                    luaL_error(L, "invalid use of '%c' in replacement string", L_ESC);
                luaL_addchar(b, news[i]);
            }
            else if (news[i] == '0')
                luaL_addlstring(b, s, e - s);
            else
            {
                push_onecapture(ms, news[i] - '1', s, e);
                luaL_tolstring(L, -1, NULL);  /* if number, convert it to string */
                lua_remove(L, -2);  /* remove original value */
                luaL_addvalue(b);  /* add capture to accumulated result */
            }
        }
    }
}


static void add_value(MatchState *ms, luaL_Buffer *b, const char *s,
                      const char *e, int tr)
{
    lua_State *L = ms->L;
    switch (tr)
    {
    case LUA_TFUNCTION:
    {
        int n;
        lua_pushvalue(L, 3);
        n = push_captures(ms, s, e);
        lua_call(L, n, 1);
        break;
    }
    case LUA_TTABLE:
    {
        push_onecapture(ms, 0, s, e);
        lua_gettable(L, 3);
        break;
    }
    default:    /* LUA_TNUMBER or LUA_TSTRING */
    {
        add_s(ms, b, s, e);
        return;
    }
    }
    if (!lua_toboolean(L, -1))    /* nil or false? */
    {
        lua_pop(L, 1);
        lua_pushlstring(L, s, e - s);  /* keep original text */
    }
    else if (!lua_isstring(L, -1))
        luaL_error(L, "invalid replacement value (a %s)", luaL_typename(L, -1));
    luaL_addvalue(b);  /* add result to accumulator */
}


static int str_gsub(lua_State *L)
{
    size_t srcl, lp;
    const char *src = luaL_checklstring(L, 1, &srcl);  /* subject */
    const char *p = luaL_checklstring(L, 2, &lp);  /* pattern */
    const char *lastmatch = NULL;  /* end of last match */
    int tr = lua_type(L, 3);  /* replacement type */
    lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1);  /* max replacements */
    int anchor = (*p == '^');
    lua_Integer n = 0;  /* replacement count */
    MatchState ms;
    luaL_Buffer b;
    luaL_argcheck(L, tr == LUA_TNUMBER || tr == LUA_TSTRING ||
                  tr == LUA_TFUNCTION || tr == LUA_TTABLE, 3,
                  "string/function/table expected");
    luaL_buffinit(L, &b);
    if (anchor)
    {
        p++;
        lp--;  /* skip anchor character */
    }
    prepstate(&ms, L, src, srcl, p, lp);
    while (n < max_s)
    {
        const char *e;
        reprepstate(&ms);  /* (re)prepare state for new match */
        if ((e = match(&ms, src, p)) != NULL && e != lastmatch)    /* match? */
        {
            n++;
            add_value(&ms, &b, src, e, tr);  /* add replacement to buffer */
            src = lastmatch = e;
        }
        else if (src < ms.src_end)  /* otherwise, skip one character */
            luaL_addchar(&b, *src++);
        else break;  /* end of subject */
        if (anchor) break;
    }
    luaL_addlstring(&b, src, ms.src_end - src);
    luaL_pushresult(&b);
    lua_pushinteger(L, n);  /* number of substitutions */
    return 2;
}

/* }====================================================== */



/*
** {======================================================
** STRING FORMAT
** =======================================================
*/

#if !defined(lua_number2strx)   /* { */

/*
** Hexadecimal floating-point formatter
*/

#include <math.h>

#define SIZELENMOD  (sizeof(LUA_NUMBER_FRMLEN)/sizeof(char))


/*
** Number of bits that goes into the first digit. It can be any value
** between 1 and 4; the following definition tries to align the number
** to nibble boundaries by making what is left after that first digit a
** multiple of 4.
*/
#define L_NBFD      ((l_mathlim(MANT_DIG) - 1)%4 + 1)


/*
** Add integer part of 'x' to buffer and return new 'x'
*/
static lua_Number adddigit(char *buff, int n, lua_Number x)
{
    lua_Number dd = l_mathop(floor)(x);  /* get integer part from 'x' */
    int d = (int)dd;
    buff[n] = (d < 10 ? d + '0' : d - 10 + 'a');  /* add to buffer */
    return x - dd;  /* return what is left */
}


static int num2straux(char *buff, int sz, lua_Number x)
{
    /* if 'inf' or 'NaN', format it like '%g' */
    if (x != x || x == (lua_Number)HUGE_VAL || x == -(lua_Number)HUGE_VAL)
        return l_sprintf(buff, sz, LUA_NUMBER_FMT, (LUAI_UACNUMBER)x);
    else if (x == 0)    /* can be -0... */
    {
        /* create "0" or "-0" followed by exponent */
        return l_sprintf(buff, sz, LUA_NUMBER_FMT "x0p+0", (LUAI_UACNUMBER)x);
    }
    else
    {
        int e;
        lua_Number m = l_mathop(frexp)(x, &e);  /* 'x' fraction and exponent */
        int n = 0;  /* character count */
        if (m < 0)    /* is number negative? */
        {
            buff[n++] = '-';  /* add signal */
            m = -m;  /* make it positive */
        }
        buff[n++] = '0';
        buff[n++] = 'x';  /* add "0x" */
        m = adddigit(buff, n++, m * (1 << L_NBFD));  /* add first digit */
        e -= L_NBFD;  /* this digit goes before the radix point */
        if (m > 0)    /* more digits? */
        {
            buff[n++] = lua_getlocaledecpoint();  /* add radix point */
            do    /* add as many digits as needed */
            {
                m = adddigit(buff, n++, m * 16);
            }
            while (m > 0);
        }
        n += l_sprintf(buff + n, sz - n, "p%+d", e);  /* add exponent */
        lua_assert(n < sz);
        return n;
    }
}


static int lua_number2strx(lua_State *L, char *buff, int sz,
                           const char *fmt, lua_Number x)
{
    int n = num2straux(buff, sz, x);
    if (fmt[SIZELENMOD] == 'A')
    {
        int i;
        for (i = 0; i < n; i++)
            buff[i] = toupper(uchar(buff[i]));
    }
    else if (fmt[SIZELENMOD] != 'a')
        luaL_error(L, "modifiers for format '%%a'/'%%A' not implemented");
    return n;
}

#endif              /* } */


/*
** Maximum size of each formatted item. This maximum size is produced
** by format('%.99f', -maxfloat), and is equal to 99 + 3 ('-', '.',
** and '\0') + number of decimal digits to represent maxfloat (which
** is maximum exponent + 1). (99+3+1 then rounded to 120 for "extra
** expenses", such as locale-dependent stuff)
*/
#define MAX_ITEM        (120 + l_mathlim(MAX_10_EXP))


/* valid flags in a format specification */
#define FLAGS   "-+ #0"

/*
** maximum size of each format specification (such as "%-099.99d")
*/
#define MAX_FORMAT  32


static void addquoted(luaL_Buffer *b, const char *s, size_t len)
{
    luaL_addchar(b, '"');
    while (len--)
    {
        if (*s == '"' || *s == '\\' || *s == '\n')
        {
            luaL_addchar(b, '\\');
            luaL_addchar(b, *s);
        }
        else if (iscntrl(uchar(*s)))
        {
            char buff[10];
            if (!isdigit(uchar(*(s + 1))))
                l_sprintf(buff, sizeof(buff), "\\%d", (int)uchar(*s));
            else
                l_sprintf(buff, sizeof(buff), "\\%03d", (int)uchar(*s));
            luaL_addstring(b, buff);
        }
        else
            luaL_addchar(b, *s);
        s++;
    }
    luaL_addchar(b, '"');
}


/*
** Ensures the 'buff' string uses a dot as the radix character.
*/
static void checkdp(char *buff, int nb)
{
    if (memchr(buff, '.', nb) == NULL)    /* no dot? */
    {
        char point = lua_getlocaledecpoint();  /* try locale point */
        char *ppoint = (char *)memchr(buff, point, nb);
        if (ppoint) *ppoint = '.';  /* change it to a dot */
    }
}


static void addliteral(lua_State *L, luaL_Buffer *b, int arg)
{
    switch (lua_type(L, arg))
    {
    case LUA_TSTRING:
    {
        size_t len;
        const char *s = lua_tolstring(L, arg, &len);
        addquoted(b, s, len);
        break;
    }
    case LUA_TNUMBER:
    {
        char *buff = luaL_prepbuffsize(b, MAX_ITEM);
        int nb;
        if (!lua_isinteger(L, arg))    /* float? */
        {
            lua_Number n = lua_tonumber(L, arg);  /* write as hexa ('%a') */
            nb = lua_number2strx(L, buff, MAX_ITEM, "%" LUA_NUMBER_FRMLEN "a", n);
            checkdp(buff, nb);  /* ensure it uses a dot */
        }
        else    /* integers */
        {
            lua_Integer n = lua_tointeger(L, arg);
            const char *format = (n == LUA_MININTEGER)  /* corner case? */
                                 ? "0x%" LUA_INTEGER_FRMLEN "x"  /* use hexa */
                                 : LUA_INTEGER_FMT;  /* else use default format */
            nb = l_sprintf(buff, MAX_ITEM, format, (LUAI_UACINT)n);
        }
        luaL_addsize(b, nb);
        break;
    }
    case LUA_TNIL:
    case LUA_TBOOLEAN:
    {
        luaL_tolstring(L, arg, NULL);
        luaL_addvalue(b);
        break;
    }
    default:
    {
        luaL_argerror(L, arg, "value has no literal form");
    }
    }
}


static const char *scanformat(lua_State *L, const char *strfrmt, char *form)
{
    const char *p = strfrmt;
    while (*p != '\0' && strchr(FLAGS, *p) != NULL) p++;  /* skip flags */
    if ((size_t)(p - strfrmt) >= sizeof(FLAGS) / sizeof(char))
        luaL_error(L, "invalid format (repeated flags)");
    if (isdigit(uchar(*p))) p++;  /* skip width */
    if (isdigit(uchar(*p))) p++;  /* (2 digits at most) */
    if (*p == '.')
    {
        p++;
        if (isdigit(uchar(*p))) p++;  /* skip precision */
        if (isdigit(uchar(*p))) p++;  /* (2 digits at most) */
    }
    if (isdigit(uchar(*p)))
        luaL_error(L, "invalid format (width or precision too long)");
    *(form++) = '%';
    memcpy(form, strfrmt, ((p - strfrmt) + 1) * sizeof(char));
    form += (p - strfrmt) + 1;
    *form = '\0';
    return p;
}


/*
** add length modifier into formats
*/
static void addlenmod(char *form, const char *lenmod)
{
    size_t l = strlen(form);
    size_t lm = strlen(lenmod);
    char spec = form[l - 1];
    strcpy(form + l - 1, lenmod);
    form[l + lm - 1] = spec;
    form[l + lm] = '\0';
}


static int str_format(lua_State *L)
{
    int top = lua_gettop(L);
    int arg = 1;
    size_t sfl;
    const char *strfrmt = luaL_checklstring(L, arg, &sfl);
    const char *strfrmt_end = strfrmt + sfl;
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    while (strfrmt < strfrmt_end)
    {
        if (*strfrmt != L_ESC)
            luaL_addchar(&b, *strfrmt++);
        else if (*++strfrmt == L_ESC)
            luaL_addchar(&b, *strfrmt++);  /* %% */
        else   /* format item */
        {
            char form[MAX_FORMAT];  /* to store the format ('%...') */
            char *buff = luaL_prepbuffsize(&b, MAX_ITEM);  /* to put formatted item */
            int nb = 0;  /* number of bytes in added item */
            if (++arg > top)
                luaL_argerror(L, arg, "no value");
            strfrmt = scanformat(L, strfrmt, form);
            switch (*strfrmt++)
            {
            case 'c':
            {
                nb = l_sprintf(buff, MAX_ITEM, form, (int)luaL_checkinteger(L, arg));
                break;
            }
            case 'd':
            case 'i':
            case 'o':
            case 'u':
            case 'x':
            case 'X':
            {
                lua_Integer n = luaL_checkinteger(L, arg);
                addlenmod(form, LUA_INTEGER_FRMLEN);
                nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACINT)n);
                break;
            }
            case 'a':
            case 'A':
                addlenmod(form, LUA_NUMBER_FRMLEN);
                nb = lua_number2strx(L, buff, MAX_ITEM, form,
                                     luaL_checknumber(L, arg));
                break;
            case 'e':
            case 'E':
            case 'f':
            case 'g':
            case 'G':
            {
                lua_Number n = luaL_checknumber(L, arg);
                addlenmod(form, LUA_NUMBER_FRMLEN);
                nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACNUMBER)n);
                break;
            }
            case 'q':
            {
                addliteral(L, &b, arg);
                break;
            }
            case 's':
            {
                size_t l;
                const char *s = luaL_tolstring(L, arg, &l);
                if (form[2] == '\0')  /* no modifiers? */
                    luaL_addvalue(&b);  /* keep entire string */
                else
                {
                    luaL_argcheck(L, l == strlen(s), arg, "string contains zeros");
                    if (!strchr(form, '.') && l >= 100)
                    {
                        /* no precision and string is too long to be formatted */
                        luaL_addvalue(&b);  /* keep entire string */
                    }
                    else    /* format the string into 'buff' */
                    {
                        nb = l_sprintf(buff, MAX_ITEM, form, s);
                        lua_pop(L, 1);  /* remove result from 'luaL_tolstring' */
                    }
                }
                break;
            }
            default:    /* also treat cases 'pnLlh' */
            {
                return luaL_error(L, "invalid option '%%%c' to 'format'",
                                  *(strfrmt - 1));
            }
            }
            lua_assert(nb < MAX_ITEM);
            luaL_addsize(&b, nb);
        }
    }
    luaL_pushresult(&b);
    return 1;
}

/* }====================================================== */


/*
** {======================================================
** PACK/UNPACK
** =======================================================
*/


/* value used for padding */
#if !defined(LUAL_PACKPADBYTE)
#define LUAL_PACKPADBYTE        0x00
#endif

/* maximum size for the binary representation of an integer */
#define MAXINTSIZE  16

/* number of bits in a character */
#define NB  CHAR_BIT

/* mask for one character (NB 1's) */
#define MC  ((1 << NB) - 1)

/* size of a lua_Integer */
#define SZINT   ((int)sizeof(lua_Integer))


/* dummy union to get native endianness */
static const union
{
    int dummy;
    char little;  /* true iff machine is little endian */
} nativeendian = {1};


/* dummy structure to get native alignment requirements */
struct cD
{
    char c;
    union
    {
        double d;
        void *p;
        lua_Integer i;
        lua_Number n;
    } u;
};

#define MAXALIGN    (offsetof(struct cD, u))


/*
** Union for serializing floats
*/
typedef union Ftypes
{
    float f;
    double d;
    lua_Number n;
    char buff[5 * sizeof(lua_Number)];  /* enough for any float type */
} Ftypes;


/*
** information to pack/unpack stuff
*/
typedef struct Header
{
    lua_State *L;
    int islittle;
    int maxalign;
} Header;


/*
** options for pack/unpack
*/
typedef enum KOption
{
    Kint,     /* signed integers */
    Kuint,    /* unsigned integers */
    Kfloat,   /* floating-point numbers */
    Kchar,    /* fixed-length strings */
    Kstring,  /* strings with prefixed length */
    Kzstr,    /* zero-terminated strings */
    Kpadding, /* padding */
    Kpaddalign,   /* padding for alignment */
    Knop      /* no-op (configuration or spaces) */
} KOption;


/*
** Read an integer numeral from string 'fmt' or return 'df' if
** there is no numeral
*/
static int digit(int c)
{
    return '0' <= c && c <= '9';
}

static int getnum(const char **fmt, int df)
{
    if (!digit(**fmt))  /* no number? */
        return df;  /* return default value */
    else
    {
        int a = 0;
        do
        {
            a = a * 10 + (*((*fmt)++) - '0');
        }
        while (digit(**fmt) && a <= ((int)MAXSIZE - 9) / 10);
        return a;
    }
}


/*
** Read an integer numeral and raises an error if it is larger
** than the maximum size for integers.
*/
static int getnumlimit(Header *h, const char **fmt, int df)
{
    int sz = getnum(fmt, df);
    if (sz > MAXINTSIZE || sz <= 0)
        luaL_error(h->L, "integral size (%d) out of limits [1,%d]",
                   sz, MAXINTSIZE);
    return sz;
}


/*
** Initialize Header
*/
static void initheader(lua_State *L, Header *h)
{
    h->L = L;
    h->islittle = nativeendian.little;
    h->maxalign = 1;
}


/*
** Read and classify next option. 'size' is filled with option's size.
*/
static KOption getoption(Header *h, const char **fmt, int *size)
{
    int opt = *((*fmt)++);
    *size = 0;  /* default */
    switch (opt)
    {
    case 'b':
        *size = sizeof(char);
        return Kint;
    case 'B':
        *size = sizeof(char);
        return Kuint;
    case 'h':
        *size = sizeof(short);
        return Kint;
    case 'H':
        *size = sizeof(short);
        return Kuint;
    case 'l':
        *size = sizeof(long);
        return Kint;
    case 'L':
        *size = sizeof(long);
        return Kuint;
    case 'j':
        *size = sizeof(lua_Integer);
        return Kint;
    case 'J':
        *size = sizeof(lua_Integer);
        return Kuint;
    case 'T':
        *size = sizeof(size_t);
        return Kuint;
    case 'f':
        *size = sizeof(float);
        return Kfloat;
    case 'd':
        *size = sizeof(double);
        return Kfloat;
    case 'n':
        *size = sizeof(lua_Number);
        return Kfloat;
    case 'i':
        *size = getnumlimit(h, fmt, sizeof(int));
        return Kint;
    case 'I':
        *size = getnumlimit(h, fmt, sizeof(int));
        return Kuint;
    case 's':
        *size = getnumlimit(h, fmt, sizeof(size_t));
        return Kstring;
    case 'c':
        *size = getnum(fmt, -1);
        if (*size == -1)
            luaL_error(h->L, "missing size for format option 'c'");
        return Kchar;
    case 'z':
        return Kzstr;
    case 'x':
        *size = 1;
        return Kpadding;
    case 'X':
        return Kpaddalign;
    case ' ':
        break;
    case '<':
        h->islittle = 1;
        break;
    case '>':
        h->islittle = 0;
        break;
    case '=':
        h->islittle = nativeendian.little;
        break;
    case '!':
        h->maxalign = getnumlimit(h, fmt, MAXALIGN);
        break;
    default:
        luaL_error(h->L, "invalid format option '%c'", opt);
    }
    return Knop;
}


/*
** Read, classify, and fill other details about the next option.
** 'psize' is filled with option's size, 'notoalign' with its
** alignment requirements.
** Local variable 'size' gets the size to be aligned. (Kpadal option
** always gets its full alignment, other options are limited by
** the maximum alignment ('maxalign'). Kchar option needs no alignment
** despite its size.
*/
static KOption getdetails(Header *h, size_t totalsize,
                          const char **fmt, int *psize, int *ntoalign)
{
    KOption opt = getoption(h, fmt, psize);
    int align = *psize;  /* usually, alignment follows size */
    if (opt == Kpaddalign)    /* 'X' gets alignment from following option */
    {
        if (**fmt == '\0' || getoption(h, fmt, &align) == Kchar || align == 0)
            luaL_argerror(h->L, 1, "invalid next option for option 'X'");
    }
    if (align <= 1 || opt == Kchar)  /* need no alignment? */
        *ntoalign = 0;
    else
    {
        if (align > h->maxalign)  /* enforce maximum alignment */
            align = h->maxalign;
        if ((align & (align - 1)) != 0)  /* is 'align' not a power of 2? */
            luaL_argerror(h->L, 1, "format asks for alignment not power of 2");
        *ntoalign = (align - (int)(totalsize & (align - 1))) & (align - 1);
    }
    return opt;
}


/*
** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
** The final 'if' handles the case when 'size' is larger than
** the size of a Lua integer, correcting the extra sign-extension
** bytes if necessary (by default they would be zeros).
*/
static void packint(luaL_Buffer *b, lua_Unsigned n,
                    int islittle, int size, int neg)
{
    char *buff = luaL_prepbuffsize(b, size);
    int i;
    buff[islittle ? 0 : size - 1] = (char)(n & MC);  /* first byte */
    for (i = 1; i < size; i++)
    {
        n >>= NB;
        buff[islittle ? i : size - 1 - i] = (char)(n & MC);
    }
    if (neg && size > SZINT)    /* negative number need sign extension? */
    {
        for (i = SZINT; i < size; i++)  /* correct extra bytes */
            buff[islittle ? i : size - 1 - i] = (char)MC;
    }
    luaL_addsize(b, size);  /* add result to buffer */
}


/*
** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
** given 'islittle' is different from native endianness.
*/
static void copywithendian(volatile char *dest, volatile const char *src,
                           int size, int islittle)
{
    if (islittle == nativeendian.little)
    {
        while (size-- != 0)
            *(dest++) = *(src++);
    }
    else
    {
        dest += size - 1;
        while (size-- != 0)
            *(dest--) = *(src++);
    }
}


static int str_pack(lua_State *L)
{
    luaL_Buffer b;
    Header h;
    const char *fmt = luaL_checkstring(L, 1);  /* format string */
    int arg = 1;  /* current argument to pack */
    size_t totalsize = 0;  /* accumulate total size of result */
    initheader(L, &h);
    lua_pushnil(L);  /* mark to separate arguments from string buffer */
    luaL_buffinit(L, &b);
    while (*fmt != '\0')
    {
        int size, ntoalign;
        KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
        totalsize += ntoalign + size;
        while (ntoalign-- > 0)
            luaL_addchar(&b, LUAL_PACKPADBYTE);  /* fill alignment */
        arg++;
        switch (opt)
        {
        case Kint:    /* signed integers */
        {
            lua_Integer n = luaL_checkinteger(L, arg);
            if (size < SZINT)    /* need overflow check? */
            {
                lua_Integer lim = (lua_Integer)1 << ((size * NB) - 1);
                luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
            }
            packint(&b, (lua_Unsigned)n, h.islittle, size, (n < 0));
            break;
        }
        case Kuint:    /* unsigned integers */
        {
            lua_Integer n = luaL_checkinteger(L, arg);
            if (size < SZINT)  /* need overflow check? */
                luaL_argcheck(L, (lua_Unsigned)n < ((lua_Unsigned)1 << (size * NB)),
                              arg, "unsigned overflow");
            packint(&b, (lua_Unsigned)n, h.islittle, size, 0);
            break;
        }
        case Kfloat:    /* floating-point options */
        {
            volatile Ftypes u;
            char *buff = luaL_prepbuffsize(&b, size);
            lua_Number n = luaL_checknumber(L, arg);  /* get argument */
            if (size == sizeof(u.f)) u.f = (float)n;  /* copy it into 'u' */
            else if (size == sizeof(u.d)) u.d = (double)n;
            else u.n = n;
            /* move 'u' to final result, correcting endianness if needed */
            copywithendian(buff, u.buff, size, h.islittle);
            luaL_addsize(&b, size);
            break;
        }
        case Kchar:    /* fixed-size string */
        {
            size_t len;
            const char *s = luaL_checklstring(L, arg, &len);
            luaL_argcheck(L, len <= (size_t)size, arg,
                          "string longer than given size");
            luaL_addlstring(&b, s, len);  /* add string */
            while (len++ < (size_t)size)  /* pad extra space */
                luaL_addchar(&b, LUAL_PACKPADBYTE);
            break;
        }
        case Kstring:    /* strings with length count */
        {
            size_t len;
            const char *s = luaL_checklstring(L, arg, &len);
            luaL_argcheck(L, size >= (int)sizeof(size_t) ||
                          len < ((size_t)1 << (size * NB)),
                          arg, "string length does not fit in given size");
            packint(&b, (lua_Unsigned)len, h.islittle, size, 0);  /* pack length */
            luaL_addlstring(&b, s, len);
            totalsize += len;
            break;
        }
        case Kzstr:    /* zero-terminated string */
        {
            size_t len;
            const char *s = luaL_checklstring(L, arg, &len);
            luaL_argcheck(L, strlen(s) == len, arg, "string contains zeros");
            luaL_addlstring(&b, s, len);
            luaL_addchar(&b, '\0');  /* add zero at the end */
            totalsize += len + 1;
            break;
        }
        case Kpadding:
            luaL_addchar(&b, LUAL_PACKPADBYTE);  /* FALLTHROUGH */
        case Kpaddalign:
        case Knop:
            arg--;  /* undo increment */
            break;
        }
    }
    luaL_pushresult(&b);
    return 1;
}


static int str_packsize(lua_State *L)
{
    Header h;
    const char *fmt = luaL_checkstring(L, 1);  /* format string */
    size_t totalsize = 0;  /* accumulate total size of result */
    initheader(L, &h);
    while (*fmt != '\0')
    {
        int size, ntoalign;
        KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
        size += ntoalign;  /* total space used by option */
        luaL_argcheck(L, totalsize <= MAXSIZE - size, 1,
                      "format result too large");
        totalsize += size;
        switch (opt)
        {
        case Kstring:  /* strings with length count */
        case Kzstr:    /* zero-terminated string */
            luaL_argerror(L, 1, "variable-length format");
            /* call never return, but to avoid warnings: *//* FALLTHROUGH */
        default:
            break;
        }
    }
    lua_pushinteger(L, (lua_Integer)totalsize);
    return 1;
}


/*
** Unpack an integer with 'size' bytes and 'islittle' endianness.
** If size is smaller than the size of a Lua integer and integer
** is signed, must do sign extension (propagating the sign to the
** higher bits); if size is larger than the size of a Lua integer,
** it must check the unread bytes to see whether they do not cause an
** overflow.
*/
static lua_Integer unpackint(lua_State *L, const char *str,
                             int islittle, int size, int issigned)
{
    lua_Unsigned res = 0;
    int i;
    int limit = (size  <= SZINT) ? size : SZINT;
    for (i = limit - 1; i >= 0; i--)
    {
        res <<= NB;
        res |= (lua_Unsigned)(unsigned char)str[islittle ? i : size - 1 - i];
    }
    if (size < SZINT)    /* real size smaller than lua_Integer? */
    {
        if (issigned)    /* needs sign extension? */
        {
            lua_Unsigned mask = (lua_Unsigned)1 << (size * NB - 1);
            res = ((res ^ mask) - mask);  /* do sign extension */
        }
    }
    else if (size > SZINT)    /* must check unread bytes */
    {
        int mask = (!issigned || (lua_Integer)res >= 0) ? 0 : MC;
        for (i = limit; i < size; i++)
        {
            if ((unsigned char)str[islittle ? i : size - 1 - i] != mask)
                luaL_error(L, "%d-byte integer does not fit into Lua Integer", size);
        }
    }
    return (lua_Integer)res;
}


static int str_unpack(lua_State *L)
{
    Header h;
    const char *fmt = luaL_checkstring(L, 1);
    size_t ld;
    const char *data = luaL_checklstring(L, 2, &ld);
    size_t pos = (size_t)posrelat(luaL_optinteger(L, 3, 1), ld) - 1;
    int n = 0;  /* number of results */
    luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
    initheader(L, &h);
    while (*fmt != '\0')
    {
        int size, ntoalign;
        KOption opt = getdetails(&h, pos, &fmt, &size, &ntoalign);
        if ((size_t)ntoalign + size > ~pos || pos + ntoalign + size > ld)
            luaL_argerror(L, 2, "data string too short");
        pos += ntoalign;  /* skip alignment */
        /* stack space for item + next position */
        luaL_checkstack(L, 2, "too many results");
        n++;
        switch (opt)
        {
        case Kint:
        case Kuint:
        {
            lua_Integer res = unpackint(L, data + pos, h.islittle, size,
                                        (opt == Kint));
            lua_pushinteger(L, res);
            break;
        }
        case Kfloat:
        {
            volatile Ftypes u;
            lua_Number num;
            copywithendian(u.buff, data + pos, size, h.islittle);
            if (size == sizeof(u.f)) num = (lua_Number)u.f;
            else if (size == sizeof(u.d)) num = (lua_Number)u.d;
            else num = u.n;
            lua_pushnumber(L, num);
            break;
        }
        case Kchar:
        {
            lua_pushlstring(L, data + pos, size);
            break;
        }
        case Kstring:
        {
            size_t len = (size_t)unpackint(L, data + pos, h.islittle, size, 0);
            luaL_argcheck(L, pos + len + size <= ld, 2, "data string too short");
            lua_pushlstring(L, data + pos + size, len);
            pos += len;  /* skip string */
            break;
        }
        case Kzstr:
        {
            size_t len = (int)strlen(data + pos);
            lua_pushlstring(L, data + pos, len);
            pos += len + 1;  /* skip string plus final '\0' */
            break;
        }
        case Kpaddalign:
        case Kpadding:
        case Knop:
            n--;  /* undo increment */
            break;
        }
        pos += size;
    }
    lua_pushinteger(L, pos + 1);  /* next position */
    return n + 1;
}

/* }====================================================== */


static const luaL_Reg strlib[] =
{
    {"byte", str_byte},
    {"char", str_char},
    {"dump", str_dump},
    {"find", str_find},
    {"format", str_format},
    {"gmatch", gmatch},
    {"gsub", str_gsub},
    {"len", str_len},
    {"lower", str_lower},
    {"match", str_match},
    {"rep", str_rep},
    {"reverse", str_reverse},
    {"sub", str_sub},
    {"upper", str_upper},
    {"pack", str_pack},
    {"packsize", str_packsize},
    {"unpack", str_unpack},
    {NULL, NULL}
};


static void createmetatable(lua_State *L)
{
    lua_createtable(L, 0, 1);  /* table to be metatable for strings */
    lua_pushliteral(L, "");  /* dummy string */
    lua_pushvalue(L, -2);  /* copy table */
    lua_setmetatable(L, -2);  /* set table as metatable for strings */
    lua_pop(L, 1);  /* pop dummy string */
    lua_pushvalue(L, -2);  /* get string library */
    lua_setfield(L, -2, "__index");  /* metatable.__index = string */
    lua_pop(L, 1);  /* pop metatable */
}


/*
** Open string library
*/
LUAMOD_API int luaopen_string(lua_State *L)
{
    luaL_newlib(L, strlib);
    createmetatable(L);
    return 1;
}

